January 2, 2020 • 43 mins
Why does the universe seem to be left-handed?
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Speaker 1 (00:08):
Hey, Jorge, remember when we talked about particles spin trying
not to remember you mean, you mean the spin that
isn't really a spin. Yeah, And then we talked about
particle color. Huh, the color that isn't actually a color.
And particle flavors. You mean the flavor that doesn't actually
(00:29):
taste like anything. That's the one. Well, I got some
news for you. Turns out particles can be left handed
or right handed. Hi am orhandmade cartoonists and the creator
(00:57):
of PhD comics. I'm Daniel, I'm a particle physicist, and
I'm mostly right handed. And welcome to our podcast Daniel
and Jorge give weird names to particle properties in the Universe,
a production of I Heart Radio, in which we do
our best to connect the weird, the strange, the amazing,
the bonkers universe that we find ourselves in. Two things
(01:19):
that actually do make sense to you, that are familiar
in every day Yeah, Because I think sometimes the universe
does feel really familiar, you know, and relatable, and I
feel like I understand it. But sometimes I feel like
the universe is this crazy, unknowable, confusing and totally unintuitive
thing that we're all living in. I mean, every time
you leave your house, every time I turn on the news.
(01:42):
If I just stay in my living room, everything feels
so familiar. Why do I have to go outside? Yeah,
but I guess. I mean, you know, sometimes the universe
and you know, particles and stars and black holes behaving
ways that really are don't make a lot of sense
to me. Yeah, and it's fast dating. How as humans
we try to make sense of them in terms of
(02:03):
things that we do understand, Like we talk about the
life cycle of stars, even though of course stars are
not alive, but you know, they begin and they burn
and then they die spectacularly, Like I hope I will
die spectacularly one day. I think most people wish for
quiet death. Daniel not a spectacular who wants to go
(02:24):
out with a whimper man. I want to end with
a supernova that sounds just like a physics super villain
Daniel in a comic book. Look, my budget from my
funeral is not like all coffins and flowers and stuff.
It's all sticks of dynamite. Great, I'll be sure to
turn on that invitation, all right, um, But the point
(02:47):
is that we do our best to understand this weird,
cold lifeless, dramatic world in terms of things that do
make sense to us. You know, we think of particles
as little balls. We think of photons is like waves
in the ocean. We think of things as having a
life cycle. What else can we do? We try to
map the universe into things that we know. Yeah, and
so today we'll be talking about a particular property of
(03:09):
the universe, or I guess particles in particular. Is that
a good way to say it? Say it, um, particular
particle property. Oh my goodness, I feel like we're I'm
talking to my kids and they're giving me a riddle.
Peter Piper picked a pack of pickled peppers. Peter Piper
picked a pack of pickle particles. Yeah, we'll be talking
(03:29):
about a really amazing particle property that we might not
even discovered if it didn't turn out that the universe
preferred one kind rather than the other. Yeah, sometimes the
universe has a preference. You know, it's just, um, it's
just the way it is. Is it just the way
it is? It the kind of thing that makes us wonder, like,
why is the universe this way and not the other way?
Every time the universe has to make a choice and
(03:50):
it chooses one direction over the other, um one place
over another, makes us wonder why this and not something else. Yeah,
So usually is as physicists, we like when the universe
is balanced, when it's symmetric and it doesn't make a preference,
because then we don't have to know why. But every
time it does make a choice, that's a clue. It
tells us there's something weird in particular about our universe.
(04:12):
It could have been different, right, and so to be
on the podcast, we'll be talking about is the universe
left handed? M hm? Why didn't we say is the
universe right handed? Yeah? Well, because the universe does have
a preference, and it turns out it's not the same
(04:33):
as a biology interesting, so meaning that the universe is
maybe not the perfect symmetrical, un judgmental thing that we
kind of wish it were, right, I mean, you wish
it weren't. Well, we're always looking for symmetries in the
universe and wondering what those means. We have lots of
really deep symmetries, like we don't think it matters where
(04:54):
in the universe you are. The laws of physics should
be the same if you're here or if you're there
or you're somewhere else the same way, there's no preferred
direction in the universe, no up and down. That sort
of makes sense to us, right. We like to think
of the universe is like democratic in that way, right,
But really it's more of an electoral college kind of thing,
(05:15):
which is the source of all of our problems. You know,
that's a fascinatingly accurate description because the universe is dominated
by mostly empty space. Empty space that contributes most of
the energy of the universe, because that's where all the
dark energy is. So you no, we we are trying
really hard to stay a political on this show. We
are applying you know, reason and logic to trying to
(05:38):
understand the universe, but of course we have to map
it sometimes too, things that make sense to us. Right,
So it turns out that the universe is not perfectly symmetrical.
It does have kind of a preference for one direction
or another, and so that's what we'll be talking about
here today. We're talking about the property of particles called
handedness right left and right handedness of particles which I
(06:00):
don't actually have any hands. Well, I'll give you a
hand for that one. Particles, As we know don't have hands,
but that doesn't mean we can't talk about handedness, right,
and like we call it handedness because it's a property
we first noticed of our hands. Like if you look
at your hands, the two are not the same. Right,
your left hand your right hand are not the same.
(06:20):
And even if you put them next to each other,
is no way to like rotate your left hand to
make it look just like your right hand. They really
are differently. The pattern, the order of the fingers is
just different from one to the other. Right, there's a
our hand. My hand, right hand is not the same
as my left hand. It's like a mirror image. That
would be word if both my hands looked exactly the same.
(06:41):
Though that's kind of a disturbing saying you like symmetry,
would you prefer to have two identical hands? Um, well,
that's different than symmetry because I feel like it hands
are symmetric, but there it's like mirror symmetry. Right, there's
a difference between merror symmetry and like exact exactness. That's right,
and that's the property we're interested in here today. Things
(07:03):
that have a handedness that have a mirror symmetry, like
your hand if you put up your left hand in
the mirror, it looks just like your right hand does
in real life, but the mirror turns left handedness into
right handedness and the other way around. Right by the way,
like a sphere. A sphere doesn't have a handedness because
it looks the same in the mirror. But your hand
it does have a handedness because it looks like the
(07:23):
other one in the mirror. And so we're interested in, like,
all right, here's a symmetry, here's a property. Does universe
prefer one or the other. And we know, for example,
in people, that there are more right handers than left
handers and you and you have to wonder, like why
is that? What does that mean about biology or evolution
or something? And now we can ask that same kind
of question about particles, right, and it turns out that
(07:45):
the particles have a handedness and that the universe kind
of prefers one over the other. Yeah, it's kind of fascinating.
All right, we'll get into that, but first we want
to give a quick shout out to Chris McKinnon in England.
That's right, we gotta request from your partner, Georgia Arnold,
who says thanks for listening to the podcast and for
teaching science to others. So Chris apparently is a fan
(08:07):
of our podcast in England. So happy holidays, Chris, and
happy birthday coming up in January. Yeah, happy birthday, and
to everyone whose birthday is coming up in the next year,
which I guess includes everybody except for those four and
enough every right, I guess that's that's right. We want
to be inclusive, but we also want to be accurate, right,
And happy holidays to everyone out there, and happy non
(08:30):
holidays to all the atheists as well. Are you saying
atheists don't know holidays? I think by definition they don't
have holidays. Oh man, I don't know this is the
topic we should dive into. But um, but yeah, thanks,
And if you are interested in writing to us and
let us us know what do you think of the podcast,
please follow us on Instagram and Twitter and Facebook. All right, well,
(08:51):
let's get back on the topic here of the handedness
of the universe, and so we might say, to the
topic at hand, let's get back to the do the
bad puns? Guys, we trailed off into some holiday cheer.
We forgot to get to all out the bad puns.
But as usually what we were wondering how many people
out there knew that the universe or that particles have
(09:12):
a preference, or even an idea or or a property
called handedness. Yeah, so I walked around campus that you
see Irvine, and I asked books if they knew what
it meant for a particle to be left or right handed.
So think about it for a second. If you were
approached by a physicist on a holiday morning and you
(09:33):
were asked if you knew whether particles can be left
or right handed? What would you answer? Here's what people
had to say. Do you know what it means to
say a particle can be left handed or right handed? No? No,
they don't have hands? Well is isn't it talking about
the movement of the current? Um So that's where I
can remember from physics I took on the micro level,
(09:54):
there's certain orientations and movements happen, and do there are
going too one way or the other way? But I'm
not superfamulate with outwards unfortunately, not now doing particles with hands? Well, well,
I would guess that it has something to do like
we're like the electrons around it, maybe more to the
(10:15):
blaster to the writer or something all right. Not a
lot of people knew that particles have handedness. No, No,
it a little bit of pushback, like, nope, particles do
not have hands. I thought as well, I'm gonna give
a hand to this person here. No. So not a
lot of familiarity with this concept. Yeah, which is uh,
(10:35):
I guess, I guess I know. I knew about this
idea just from talking to you, Daniel another physicists, because
I know that it's related to like the spin of particles, right,
and how they look at each other in the mirror. Yeah,
and it's related to parody. And we did a whole
fun video with Derek Mueller of Veritassium about parody and
(10:56):
charge parody and its impact on time with particles. It's
a gorgeous video. Folks out there really interested in this
concept of symmetries and particles, go check it out. I
think it's called do Particles Tell Time? On YouTube? And
so so, just to clear things up, particles don't have hands.
We we've established that, at least we don't think that
(11:17):
we've seen, right, they could have point hands, that's right.
We have to qualify what we understand here. We have
not seen particles hands. It doesn't mean they don't have them.
They could be super duper tiny cute, little tiny particle hands. Yeah,
that's how they that's how they hold on to each other,
they do how they make those bonds. Right, that's how
(11:39):
the universe is connect the tiny little hands. That's right.
But you know, you can have handedness even if you
don't have hands, and let's get into it. But I
feel like even if particles were a little spherical balls,
which I know they're not, it seems weird that they
would have like a preference between right and left, because
what's the right and left of a perfect sphere? You're
exactly right, and um, if you had a perfect sphere,
(12:02):
it's perfect sphere is not handed. Right. To have something
be handed you need at least two different directions that
you can compare. And so a perfect sphere, however, can spin,
and when it spins, the axis along which it's spinning
gives you one direction, and then you can compare that
spin direction to something else, like the direction it's moving,
(12:23):
and you can ask, like, do those two directions line up?
This kind of stuff. So particles can have handedness because
it's built on top of other properties they have. But
You're right, a sphere that has no handedness, it looks
the same in the mirror by itself. And and as well,
I guess a point as well, right, Like a point
would have even less of a less of a hand
(12:44):
unless it has plenty point hands right, which is not
really the matter at hand. But you're saying that handedness
for particles is related to you get like you got
to throw in another property into the conversation in order
to have handedness in a point particle. Yeah, And here's
where we get into murky territory, because handedness it's a
(13:08):
quantum property with particles. It's like an intrinsic property. It's
like charge right, or it's like spin it's not physically spinning,
or there is no place where the charge is. It's
just like a label we put on a particle. And
so these particles have this intrinsic leftiness or rightness really,
and we can make it connected to this other physical thing,
(13:29):
but in the end it really is deeply, fundamentally just
sort of an internal quantum label that we can never
really truly understand. Really, because I've never seen handedness in
any of the you know, posters or graphics for the
standard model of physics. You know, I see spin, I
see charge, I see color, but I never see like
left ear righty. You know. Yeah, Well it's mostly connected
(13:51):
to the weak force, because the weak forces what revealed
to us that handedness was a thing we had to
think about and that it was actually important. So I
guess we should call it quantum handedness because that's the
that's the solution to any confusion in physics is just
at a at a word that says you're right. It
(14:12):
is confusing, It's okay, don't try to understand it at
an intuitive level. It's weird. No, you're right. Quantum X.
What we mean when we say that in physics is like, well,
this is like some other weird version of X. We're
using X because it's similar kind of in some way
to the thing you're familiar with. There's an analogy that
that's maybe helpful, but it's not really the same thing. Right.
(14:34):
It's kind of like how our podcast is known for
quantum humor. That's right, only particles get it. It's neither
here nor there, but just still try to understand it.
That's right. That's what we're getting a lot of quantum
clasks and making a lot of quantum bucks. It's it's
all theoretical, Daniel. No. But in the case of particles,
(14:57):
you can sort of define this handedness by saying, let's
look at the direction it's moving, and then let's look
at the axis around which it's spinning, and ask are
those two things pointing in the same direction or not?
And so we call it right if they're in the
same direction, and left handed if they're in opposite directions.
But that's arbitrary. We could have just labeled them any way.
(15:18):
You know. We can call them alpha and beta, or
blue and red, or left and right or right and
left right. These are just labels we deside. Oh, I see.
It'd be like saying, like, some particles like to be
positive and green, and some particles like to be negative
and blue, and you might call that handedness or some
other property. Yeah, some of the properties, but this particular
(15:39):
one that we found, it turns out the universe cares about.
So you could construct all sorts of things and column handedness,
but the universe might be like, yeah, that's fine, I
don't care about that doesn't matter to me. But this
one is interesting because the universe does seem to care
it is something that is important. It changes the way
the universe treats these particles, and so it really does matter. Okay,
(16:00):
so you're saying that handedness in a particle means that
the spin of the particle is sort of a line
to its motion. Yeah, And it's a bit confusing to
think about the direction of spin because it's going in
every direction. Right, it's a spinning thing. It's turning and
turning and turning. What if I just turned my head
upside down, wouldn't it flip it on its head? Well,
(16:20):
it wouldn't change the direction of spin. Right, But so
you use your right hand, and if your fingers are
curling the direction the particle spinning, your thumb tells you
where we sort of define the direction of the spin vector,
and it's along the axis of spin. It's kind of
like a top if you're spinning a top. M I
guess you can spin a top both ways. But it's
(16:41):
kind of a screwdriver, I guess, or like a screw
it's like clockwise versus counterclockwise. Right, you have to define
one direction or the other. And we say that the
direction that you're the fingers curl on your right hand
is a certain way, and that helps us define a
certain direction. And so if the particle is moving in
the same same direction that this spin is pointing, where
(17:02):
again the spin comes from your thumb. If your fingers
curl the way the spear is spinning, we call that
a right handed particle. Really. Yeah, So parts of particles
don't have the option of moving either way, like they
always either move in the direction of spin or not
in the direction of spin. Oh, that's fascinating question. Remember
spin is quantized, right, and so you measure spin along
(17:24):
any axis. And because it's quantized either along that axis
or in the other direction, spin is not a infinitely
valued quantity. It has to be either positive or negative.
It's quantitied. It's this quantum spin. Like let's say that
spinning and the spinning direction is up. You're saying that
particles can move up and down. They have to move
up or down. You can't say the particle is spinning
(17:46):
and its spinning direction is up. That's quantum mechanically impossible
to know the complete spin direction, right, because there's three
different axes, and you can't know spin along three axis simultaneously.
Because the Heisenberg is certain principle. Oh, boy, the you
have to go the other direction. You say, all right,
which direction is my particle moving? All right? That define
some direction. Now I can ask is it spinning along
(18:08):
that direction or in the opposite direction? I see, And
that what I get if I ask it if is
it spinning in the direction of moving or not? Is
something that particles Some particles will always give you the
one answer, and other particles will always give you the
other answers. Or is it random? Like a particle can
be moving either aligned or not aligned with its spin.
(18:29):
That's what we call handedness. If a particle is right handed,
then it's moving with its spin. If it's left handed,
it's moving away from its spin. Now, some particles, like neutrinos,
you only ever see left handed neutrinos. Right handed trinos
do not exist. Other particles you can have both a
right handed version or a left handed version. Oh, I see, alright.
(18:50):
So some particles are ambidexterous. They can right with the
right or left hand. But some particles in nature are
definitely lefties or right ease. Yeah, And it's it's a
little bit more subtle than that. It's like, do you
think of the electron and the positron is different particles
or sort of two sides of the same coin in
the same way. Do we think of like the left
(19:11):
handed electron and the right handed electron is two different
particles or just sort of like two different versions of
the electron, because it turns out nature sees them as different.
So the electron can be right or left handed, or
you could say it that there are right handed electrons
and left handed electrons. Oh, I see, but is it
like fifty fifty or what is it? Um? The universe
(19:32):
prefers left handed electrons. You mean meaning there are more
of them, There are more left handed electrons. Yes, wow,
huh so it's kind of the opposite of people. No,
that's right. And also for our DNA, you know, our
d N A has a handedness to it also, and
it's also right handed. All of our organic molecules in
our body are right handed molecules. Uh. Interesting, alright, So
(19:55):
that's kind of what handedness is is um, do particles
like to move into direct in which they spin or
do they not? Or that they like to move in
the direction which they not spin. So that's a handedness
in particles. And so let's get into what that means
for the universe is prospects in Major League Baseball, whether
there are going to be drafted early or not, and
(20:19):
why it matters maybe to you and me. But first,
let's take a quick break, all right, Danniel. So you're
saying that some particles in nature, like the electron, can
(20:40):
be right or left handed, meaning they can move. You
see them moving in the direction that they're spinning, and
some of them you see them moving not in the
direction they're spinning. But some particles, like the neutrino, do
have a preference. That's exactly right. Neutrinos are only left
handed and anti neutrinos are only right handed. And this
is a really fascinating thing that we discovered only about
(21:01):
fifty years ago, that this concept of particle handedness is
a real thing in the universe. And you know, we've
been like over the history of science adding labels to
particles as we discover them, we'll we'll see something happen
and we're like, well, we can't explain that with the
labels we currently have. So maybe particles are a little
bit more complicated, like we have to add spin to them,
(21:23):
or we have to add flavor or color or whatever
to sort of have our theory have enough wrinkles in
it to describe all the weird effects that we observe,
and so handedness is like one of the latest ones.
In the late fifties, people saw these really strange experiments
where it looked like the universe didn't work the same
in the mirror as it does not in the mirror,
(21:44):
and to explain them, they had to add this new
property to particles called handedness. Oh, I see, Like, if
every particle in nature was right and left handed, we
wouldn't even have a name for it. It could just
be like, you know, it wouldn't matter. But you're saying
it's sort of does matter in the universe. Yeah, we
wouldn't know if it was real. Like you and I
could right now invent a new particle label right, call
(22:08):
its strip nous And all right, the electrons we're gonna
say are blue stripe and with red, and those electrons
are green striped with white or whatever I'm gonna go with.
Bananan is banan is. But if the universe treats particles
the same, whether or not johe has labeled them to
be banana equals one or banan equal zero, then it
doesn't matter. It's not a physical thing, right, It's just
like an idea in your mind. It's like literally another thing.
(22:29):
Like you would say, that's not a thing, dude, but
nobody cares. But let's say somebody doesn't experiment one day
and they just and they realize, you know what particles
that Joe has little labeled having banan equals one, the
universe treats differently than we'd be like, the universe is
not symmetric to banananus, and then it would be a
real physical thing. That's exactly what happened in physics. People
(22:50):
had this idea of handedness, but they thought that's ridiculous.
How could the universe prefer one to the other. Clearly
it's symmetric. There's two options there. It's just a thing
in your head. And they didn't experiment. That proved them wrong.
It was like in Clueless, where one of them the
other stopped trying to make it a thing. It's not
a thing, but it turns out it is a thing.
(23:11):
It turns out it is a thing. And you know,
there's a lot of really interesting deep philosophical questions. They're like,
how many other things are there? Of particles? That are
really exists, but we just haven't figured out either the
way the universe prefers one to the other or an
even deeper question is what if there are particle things
that the universe is just totally symmetric to so we
(23:32):
will never discover them, Like it is a thing, but
we can't tell a thing. Yeah, in which case is
it really a thing? I think that's what's happening with
the banana is of particles. You guys just can't see it,
but I know it's there. Maybe we just need a
really big accelerator once you raise fifty dollars and we'll
discover bananan this. You wouldn't go to a circle. We're
(23:52):
just going to half circle. That's right. We need to
sort about elliptical accelerator, you know the been and a curve. Yeah,
and forget and forget those cryogetic magnets. We would just
use banana appeals to lubricate the particles. It's not a
particle accelerator. It's a particle slipper. There you go. Comedy
(24:16):
would be a plentiful in this accelerator. Yeah. Okay, so
particles have a handing this and so what does that mean?
What does that mean that the universe has the preference
in some cases or not you saying You're saying it's
related to the weak force. Yeah, Well, we have all
these fundamental forces of physics, you know, the weak force,
the strong force, electromagnetism, and gravity, and they all are
(24:39):
different forces. Were trying to understand, of course, how they're related.
But they have different effects, and most of them don't
care one whit about whether a particle is left handed
or right handed. But the weak force is weird, Like
the electromagnetic force doesn't care if an electron is right
handed or or left handed. It's democratic. It treats those
two the same, and the strong force treats left handed
(25:02):
corks and right handed corks the same way. It's like,
I see you both the same, I am handedness blind.
I'm gonna attract you or force you to do something,
and I don't care. That's right. If you didn't experiment
with the strong force, and you had it set up
next to a mirror, and you watch the experiment unfolding
in the mirror, you could use the exact same laws
(25:22):
of physics that we have in our universe to describe
what you see in the mirror. Because in the mirror universe,
all the handednesses are flipped, but the strong force doesn't care.
It's like, oh, left handed corks now are now right
hand corks? I treat him the same. Oh I see
the equations kind of work out. The same equations are
perfectly symmetric, and the effects are perfectly symmetric, so flipping
them does nothing, Like what do you see in the mirror?
(25:44):
Could may as well not be in the mirror? Yes,
or you can't do an experiment to tell are you
in the mirror world or not? As the results of
the same interest. But that's not true of the weak force. Okay,
so the weak force, it's different different. It does affect
particles differently depending on this idea of handedness. That's right.
(26:06):
And it was in the fifties of people realized nobody's
ever checked to see if the weak force breaks this
rule or not. People just sort of assumed it's such
a deeply ingrained assumption, like, of course the universe doesn't
prefer one or the other. And then the theorists went
through and said, well, has anybody ever checked? And people
had checked for a electro magnetism and for the strong
(26:26):
force and all that stuff, but nobody had checked for
for the weak force, and if physicist did it, well,
I feel like there are two ways in which handedness
can matter. Like one is which are the right or
lefties do we see more of? And that's kind of interesting,
Like the fact that we see more left handed new
trinos and right handed new trinos is sort of one
(26:49):
way that the universe is a preference. But then you're
you're I feel like there's also another way in which
the universe has a presence, which is in through the forces.
Like the laws of physics actually applied differently to the
lefties or right easy, but those are the same concepts.
Right we interact with things using forces, so we only
see left handed neutrinos because we interact with them. It's
(27:10):
possible there are right handed neutrinos out there that we
can't interact with because our forces don't touch them. We
only see what we what it's visible and what we
can interact with as a whole. You know, we won't
recently discovered that there's huge parts of the universe. We
barely have hints that actually exist, and so there could
be other particles out there that are right handed neutrinos.
We haven't seen because we can't interact with them. Oh
(27:32):
I see, it's the same thing. It's the same thing.
There could they have plot thickens or um passes throughs
like neutrinos. We're not I'm not quite sure what how
people are getting this, but we're just saying that there could.
There isn't more of the left handed neutrinos in the universe.
Is just that's the only kind we see. But we
(27:53):
don't know if there are right handed neutrinos because we
can't interact with them. Therefore, we can't prove whether or
not they exist because what we us to interact with
them has a preference. It's like a filter. Now, the
other particles, electrons and quarks, we can interact with them
in other ways that are democratic, right, because the strong
force and electromagnetism doesn't prefer one or the other. Neutrinos,
(28:14):
we can only interact with them via the weak force.
Oh I see. It's the only way we can see
them and they and it certainly does prefer it. So
there could be as many right handed nutrinos out there
in the universe as left handed neutrinos. We just can't
see them because the weak force only lets us interact
with left handed ones. That's right. And you know in
(28:34):
the same way that like the space could be filled
with invisible, imperceptible bananas, we can't see them, so are
they really there? Well, we have to use the banana force,
which I've yet to discover, but I'm sure it's it's
on the horizon there. Yeah. And it's fascinating because this
effect has to do also with charge, right, because the
(28:56):
particle that mediates this thing from the weak force, the
W particle, which carries electric charge. So you have W
minuses can decay to left handed electrons and W plus
is decay to right handed positrons. Okay, so what does
that mean. It's relevant because the way we sort of
(29:17):
patched up this symmetry is by adding charge to it.
You can tell whether or not you're in the mirror world.
By doing this experiment, um to see whether things are
reversed right, whether the weak force is giving you left
handed stuff or right handed stuff. But if you in
the mirror you also flip the charge of everything, then
the experiment looks exactly the same. Okay, Well, maybe step
(29:37):
us through a little bit, like what does it mean
that the weak force prefers left handed to right hand,
like it only interact with left handed things as far
as we know, or or like it only works with
left handed things. Yeah. The w bosons in particular will
only interact with left handed matter particles or right handed
(29:59):
antimatter articles. So left handed electrons, left handed corks, left
handed neutrinos, or right handed positrons, right handed anti neutrinos,
right handed anti corks. The z the z boson, which
is another particle that communicates the weak force, is even weirder.
It will interact with both, but it prefers the left
(30:20):
hand like interacts with the left lefties more than the rightings.
Oh you're okay, now, I guess now. Now you're taking
me through the particles that mediate that like helps us
communicate these forces. Right, that's exactly right, because the weak
forces three of them. Okay, you're saying that the particles
that communicate the weak force, those are the ones that
(30:41):
have the preference. It's not like the concept of the
weak force as a preference, but the particles that communicated
have a preference. Yeah. Well, the particles, they are the
manifestations of the force. Right, we think about these particles
as doing the duty of the force the Jedi does.
The Jedi order exists without the Jedi, you know, they're
carrying out the mark in orders, the Jedi hierarchy. So well,
(31:03):
I mean, it's it's like saying like, it's not that
the police force has a preference for left handed right
hand the people. It's more like, you know, it's like
parking offers have a preference, but uh, you know, detectives
have a different preference. You know what I mean, Like,
it's it's it's it's different than saying that the whole
thing has a preference. Yeah, and you're right. And there
are three particles there, the media, the weak force, the
(31:25):
W plus, the W minus, and the Z those are
sort of like the analogies of the photon. But for
the weak force and the W plus and the W
minus they only interact with left handed particles or right
handed antiparticles. I see. It's like that's how the preference
manifests itself. It's like the messengers for this force have
(31:45):
a preference. That's why we can't communicate with right hand
the netrinos, because the messengers are kind of blinded to
that the other kind. Yeah, and that's how they discovered it.
They took a bunch of atoms and they lined up
their spins in a certain direction, and then they saw
which do direction do the particles shootout? Do the shoot
out in the same direction of the spin, in which
case they'd be right handed. Do they shoot out against
(32:06):
the direction of the spin, in which case they'd be
left handed. And they sort of expected it to be
balanced so you couldn't tell, Like they expected to get
the same number of right and left handed particles, so
that you couldn't tell if you were in the mirror world.
But what they saw was a total shocker. Not only
was it not balanced, but it was totally unbalanced, like
zero right handed particles a left handed particles were shot out.
(32:29):
And so the weak force doesn't just prefer left handed particles,
It like maximally prefers it as far as we know.
I mean, could it be producing right hand at once
that we just can't see or interact with. It could
be there could be right handed particles that we don't
interact with, but they don't interact with the weak force,
so they have to be some other new force for
us to interact with them. If they interacted via the
weak force, we would see it. Well, but I mean,
(32:51):
I guess one question is, how do we know it's
the weak forces fault or those particles is fault? Like
what if it's our fault? You know, like what if
we were parents, it's always our fault. Yeah, what do
you mean our faults? Well, I mean, like maybe maybe
there's a new kind of boson we'll call it the
(33:11):
ex boson, which does interact with the right ten particles
through the weak force, but we just don't interact with
the ex boson. Totally possible. Yeah, there could be a
whole complicated sectors of particles out there that interact with
each other but not with us, and we just haven't
seen them or haven't yet discovered them. Nobody's invited us
to the party. That's the whole hypothesis for dark matter, right.
(33:33):
We know that there's a lot of dark matter out there.
We don't know what kind of particle is it. We
don't know if it feels forces with um among those particles,
we don't know if there's like ten different dark matter
particles are always changing into each other. So there could
be a whole complicated sectors and oceans of physics there
that we are not primy tune because we don't have
like a portal into them, no way to interact with
(33:55):
anything that's happening there. Right, If only we had that
banana particle accelerator, it would open new doors to the
universe for us. It would peel away the layers hidden
from us. It would slip us into a new era
of physics. Al Right, well, that's that. That makes it
a bit clearer for me, and how the universe has
(34:16):
this preference, and so let's get into why it matters
to the universe and maybe to us. But first let's
take a quick break, all right, Daniel, So the universe
(34:37):
apparently prefers lefties. You know, I think left handed people
always have felt pretty special, is my understanding. And now
they know why, and now they know why the universe
likes you better. Yeah, well, the weakest part of the
universe at least likes them better. Oh no, that's not true.
Gravity is the weakest force. Week the weak forse just
sort of has that name. But it it's fascinating, you know,
(35:01):
not only that the universe is asymmetric that seems to
notice that there's a handedness, but that it prefers this one,
and you can wonder, like, why don't we live in
a universe that's asymmetric the other way that prefers right
handed particles right where the weak force interacts only with
the right handed particles. It's this kind of arbitrary seeming
(35:22):
choice that makes us wonder about like the multiverse right, well, um,
meaning like maybe it's weird that it has a preference,
So there must be a twin out there who is
right handed. Well, that's the symmetry in your brain screaming
out for an explanation, right, I think there must be balanced,
but there doesn't have to be. You know, imagine you're
at the control panel of the universe in the first
(35:44):
moment of the Big Bang, when the laws of physics
are being set in stone, and you have to choose
left handed or right handed universe. You know, how is
that choice made? Are there a billion universes out there
and it's randomly assigned for each one, or is there
some deep underlying principle of physics that demand hands that
the weak force be left handed? There could be no
other way? Or could they could it just flip the coin?
(36:06):
It could be We we don't know, Like according to
our current understanding, you could write consistent laws of physics
where the weak force um prefers them equally, or the
weak force prefers only right handed particles, or were prefers
one by a little bit. We don't understand why it
is this way. Does it have to be this way?
We have no reason to believe it has to be
(36:27):
this way, and yet it is so. That seems to
me like a clue. Right, do we know in people
why some people are left handed or right handed? And
does it depend on genes or is it just some
random process um Well, based on my deep expertise in
biology from being married to biologists, is she right handed
or left hand? She's right handed, but we have some
(36:47):
lefties in her family. There's actually two layers of answer there.
One is people like what they prefer to write with,
and we're mostly right handed. We don't know why, And
it's again a great question, like was that just an
arbitrary choice that the brain decided to specialize and this
side of the brain is better at this, and the
other side of the brain is better at that, And
maybe there were equal populations at some point and then
(37:08):
it just sort of randomly drifted in one direction. We
just don't know. Um. And then there's this deeper question
about the chirality of molecules in life. All the molecules
in life, including d NA, have a corality that's right handed,
which means they have the same sort of um orientation
when you rotate the object right and like molecules have
(37:31):
a mirror image version of themselves too. Precisely, every single
organic molecules right handed. And if you were fed like
food made out of left handed molecules, you couldn't eat it,
like they die, you cannot process it. And so that's
another just like seems like an arbitrary choice could have
(37:51):
been something else. Um, we don't understand any of these things.
And I don't know if the if the mystery of
particle physics handedness is connected to those at all, because
it's definitely the other direction, or if this is just
sort of a mathematical connection where you can identify handedness
and sort of see a similarity in the sort of question. Well,
I see, huh, Like, um, like everything that might be
(38:12):
possible would have a handedness preference or something like biology
particles you know, like just a fundamental you know, property
of of existing. Yeah, but it makes our universe interesting,
and for example, the reason why the weak force is
so weird and so left handed is one of the
(38:33):
reasons why the Higgs boson is so fascinating. What do
you mean, Well, the Higgs boson, what it does is
it connects the left and right handed particles together to
give them mass. It interacts with the left and the right.
It touches, it talks to both of them, and to
talking to them together is how it gives those particles mass.
And neutrinos we don't know. We think they have mass,
(38:55):
but we don't quite really know how much mass they
have and how they get the mass, and do they
get it from the Higgs boson or not. It's a
whole bit complicated question. But the Higgs, it treats the
left and the right totally equally and sort of combines
them into one combined particle that has a specific mass. Right,
But I guess the main point is that the universe
has a preference for left or right hand. It is,
(39:16):
it seems, but we don't know why it has that preference. Right,
it's a big mystery. Right, And it's weird. Yeah, it
is weird. And if it wasn't for this little effect
in the weak force, which took a long time to discover.
We wouldn't even know, so it could have been that,
you know what if the weak force was totally symmetric
for some weird reason. Particles have handedness, but we didn't
(39:38):
even know, like that they have this property, Well, we
wouldn't care, I guess, right, I care? I care. I
want to know the truth, man, not just what's relevant
for some excises. You want to see all the features,
even if you can't see the features, of course. I
want to know what does it mean to be a particle?
All right? What are the number of labels you need
to define a particle? Mass, spin, charged, color, flavor? Why
(40:01):
all those things? What do they mean? Why this and
why not that? Why not bananimists? To me, these are
really deep, fascinating questions about like the very nature of
the universe. So yeah, I want to know, Like if
you found out half of all particles had an asterisk
next appin to them, But no, it didn't matter at
all for anything else, Like nobody would care, but you
would care me and all the other particle physicists in
(40:24):
the world, and anybody who cared about understanding the nature
of reality. But yeah, you're right. Nobody else you like,
why does that have an asterisk? I see, all right,
well I want to know why the universe has an asterisk?
All right? Well, I think this is all just a
big lesson on ways in which we explore the universe.
You know, we look for interesting phenomenon and interesting preferences
(40:48):
that the universe has, and that tells us something about
how it's all put together. Yeah, and we don't understand
the importance um and the ramifications sometimes of these things.
Like people thought about particle handedness as sort of an
abstract idea a hundred years ago when particles were first
being understood. They thought, now, whatever, it's just a mathematical curiosity.
It's not relevant, and then later turned out to be relevant,
(41:10):
and it might even turn out to be more relevant.
Maybe we'll discover a new force that's very powerful and
does prefers left to right or right to left or
something like that. So it's it's worth just sort of
like exploring and trying to understand because you never know
where the next big discovery is going to be. Yeah,
it would be pretty cool. Would you like Daniel to
have a hand in that discovery? Only, but only if
(41:34):
it's a left hand. I'd like to discover it. And
then I've got like you to give me a hand
when I did. You'd like to get both your hands
on this discovery. I just want to get my hands dirty, okay.
And that with that, we've exhausted all the bad puns, Daniel,
so maybe we should wrap it up. That's right, we've
done all the left handed punts and the right handed punts. Well,
(41:55):
thank you all for listening to me. This is a
fascinating question about the sort of deep nature of the universe,
us in this stuff that makes it up, and how
we understand it in terms of our macroscopic ways of thinking,
flavor of color, spin, and now left handedness and right handedness. Yeah,
so we hope you enjoyed that. Thanks for joining us.
On the other hand, we're not done yet. We're gonna
(42:15):
do the mirror mirror image of this podcast episode, but
the whole thing backwards, the back course, and we'll say
the universe has a preference for right handed particles. We've
got to do it backwards and positively charged. And where
the jokes are good this time, that's right, where I
(42:37):
make the jokes and you laugh at them all right,
Thanks everyone for tuning in, and I hope that podcast
reached a parody of our other ones and it's not
a parody of itself. See you next time. Before you
still have a question after listening to all these explanations,
(42:58):
please drop us a line and we'd love to hear
from you. You can find us on Facebook, Twitter, and
Instagram at Daniel and Jorge That's one Word, or email
us at Feedback at Daniel and Jorge dot com. Thanks
for listening and remember that Daniel and Jorge Explain the
Universe is a production of I Heart Radio. For more
podcast from my Heart Radio, visit the I heart Radio app,
(43:20):
Apple Podcasts, or wherever you listen to your favorite shows.
Hey, Jorge, remember when we talked about particles spin trying
not to remember you mean, you mean the spin that
isn't really a spin. Yeah, And then we talked about
particle color. Huh, the color that isn't actually a color.
And particle flavors. You mean the flavor that doesn't actually
(00:29):
taste like anything. That's the one. Well, I got some
news for you. Turns out particles can be left handed
or right handed. Hi am orhandmade cartoonists and the creator
(00:57):
of PhD comics. I'm Daniel, I'm a particle physicist, and
I'm mostly right handed. And welcome to our podcast Daniel
and Jorge give weird names to particle properties in the Universe,
a production of I Heart Radio, in which we do
our best to connect the weird, the strange, the amazing,
the bonkers universe that we find ourselves in. Two things
(01:19):
that actually do make sense to you, that are familiar
in every day Yeah, Because I think sometimes the universe
does feel really familiar, you know, and relatable, and I
feel like I understand it. But sometimes I feel like
the universe is this crazy, unknowable, confusing and totally unintuitive
thing that we're all living in. I mean, every time
you leave your house, every time I turn on the news.
(01:42):
If I just stay in my living room, everything feels
so familiar. Why do I have to go outside? Yeah,
but I guess. I mean, you know, sometimes the universe
and you know, particles and stars and black holes behaving
ways that really are don't make a lot of sense
to me. Yeah, and it's fast dating. How as humans
we try to make sense of them in terms of
(02:03):
things that we do understand, Like we talk about the
life cycle of stars, even though of course stars are
not alive, but you know, they begin and they burn
and then they die spectacularly, Like I hope I will
die spectacularly one day. I think most people wish for
quiet death. Daniel not a spectacular who wants to go
(02:24):
out with a whimper man. I want to end with
a supernova that sounds just like a physics super villain
Daniel in a comic book. Look, my budget from my
funeral is not like all coffins and flowers and stuff.
It's all sticks of dynamite. Great, I'll be sure to
turn on that invitation, all right, um, But the point
(02:47):
is that we do our best to understand this weird,
cold lifeless, dramatic world in terms of things that do
make sense to us. You know, we think of particles
as little balls. We think of photons is like waves
in the ocean. We think of things as having a
life cycle. What else can we do? We try to
map the universe into things that we know. Yeah, and
so today we'll be talking about a particular property of
(03:09):
the universe, or I guess particles in particular. Is that
a good way to say it? Say it, um, particular
particle property. Oh my goodness, I feel like we're I'm
talking to my kids and they're giving me a riddle.
Peter Piper picked a pack of pickled peppers. Peter Piper
picked a pack of pickle particles. Yeah, we'll be talking
(03:29):
about a really amazing particle property that we might not
even discovered if it didn't turn out that the universe
preferred one kind rather than the other. Yeah, sometimes the
universe has a preference. You know, it's just, um, it's
just the way it is. Is it just the way
it is? It the kind of thing that makes us wonder, like,
why is the universe this way and not the other way?
Every time the universe has to make a choice and
(03:50):
it chooses one direction over the other, um one place
over another, makes us wonder why this and not something else. Yeah,
So usually is as physicists, we like when the universe
is balanced, when it's symmetric and it doesn't make a preference,
because then we don't have to know why. But every
time it does make a choice, that's a clue. It
tells us there's something weird in particular about our universe.
(04:12):
It could have been different, right, and so to be
on the podcast, we'll be talking about is the universe
left handed? M hm? Why didn't we say is the
universe right handed? Yeah? Well, because the universe does have
a preference, and it turns out it's not the same
(04:33):
as a biology interesting, so meaning that the universe is
maybe not the perfect symmetrical, un judgmental thing that we
kind of wish it were, right, I mean, you wish
it weren't. Well, we're always looking for symmetries in the
universe and wondering what those means. We have lots of
really deep symmetries, like we don't think it matters where
(04:54):
in the universe you are. The laws of physics should
be the same if you're here or if you're there
or you're somewhere else the same way, there's no preferred
direction in the universe, no up and down. That sort
of makes sense to us, right. We like to think
of the universe is like democratic in that way, right,
But really it's more of an electoral college kind of thing,
(05:15):
which is the source of all of our problems. You know,
that's a fascinatingly accurate description because the universe is dominated
by mostly empty space. Empty space that contributes most of
the energy of the universe, because that's where all the
dark energy is. So you no, we we are trying
really hard to stay a political on this show. We
are applying you know, reason and logic to trying to
(05:38):
understand the universe, but of course we have to map
it sometimes too, things that make sense to us. Right,
So it turns out that the universe is not perfectly symmetrical.
It does have kind of a preference for one direction
or another, and so that's what we'll be talking about
here today. We're talking about the property of particles called
handedness right left and right handedness of particles which I
(06:00):
don't actually have any hands. Well, I'll give you a
hand for that one. Particles, As we know don't have hands,
but that doesn't mean we can't talk about handedness, right,
and like we call it handedness because it's a property
we first noticed of our hands. Like if you look
at your hands, the two are not the same. Right,
your left hand your right hand are not the same.
(06:20):
And even if you put them next to each other,
is no way to like rotate your left hand to
make it look just like your right hand. They really
are differently. The pattern, the order of the fingers is
just different from one to the other. Right, there's a
our hand. My hand, right hand is not the same
as my left hand. It's like a mirror image. That
would be word if both my hands looked exactly the same.
(06:41):
Though that's kind of a disturbing saying you like symmetry,
would you prefer to have two identical hands? Um, well,
that's different than symmetry because I feel like it hands
are symmetric, but there it's like mirror symmetry. Right, there's
a difference between merror symmetry and like exact exactness. That's right,
and that's the property we're interested in here today. Things
(07:03):
that have a handedness that have a mirror symmetry, like
your hand if you put up your left hand in
the mirror, it looks just like your right hand does
in real life, but the mirror turns left handedness into
right handedness and the other way around. Right by the way,
like a sphere. A sphere doesn't have a handedness because
it looks the same in the mirror. But your hand
it does have a handedness because it looks like the
(07:23):
other one in the mirror. And so we're interested in, like,
all right, here's a symmetry, here's a property. Does universe
prefer one or the other. And we know, for example,
in people, that there are more right handers than left
handers and you and you have to wonder, like why
is that? What does that mean about biology or evolution
or something? And now we can ask that same kind
of question about particles, right, and it turns out that
(07:45):
the particles have a handedness and that the universe kind
of prefers one over the other. Yeah, it's kind of fascinating.
All right, we'll get into that, but first we want
to give a quick shout out to Chris McKinnon in England.
That's right, we gotta request from your partner, Georgia Arnold,
who says thanks for listening to the podcast and for
teaching science to others. So Chris apparently is a fan
(08:07):
of our podcast in England. So happy holidays, Chris, and
happy birthday coming up in January. Yeah, happy birthday, and
to everyone whose birthday is coming up in the next year,
which I guess includes everybody except for those four and
enough every right, I guess that's that's right. We want
to be inclusive, but we also want to be accurate, right,
And happy holidays to everyone out there, and happy non
(08:30):
holidays to all the atheists as well. Are you saying
atheists don't know holidays? I think by definition they don't
have holidays. Oh man, I don't know this is the
topic we should dive into. But um, but yeah, thanks,
And if you are interested in writing to us and
let us us know what do you think of the podcast,
please follow us on Instagram and Twitter and Facebook. All right, well,
(08:51):
let's get back on the topic here of the handedness
of the universe, and so we might say, to the
topic at hand, let's get back to the do the
bad puns? Guys, we trailed off into some holiday cheer.
We forgot to get to all out the bad puns.
But as usually what we were wondering how many people
out there knew that the universe or that particles have
(09:12):
a preference, or even an idea or or a property
called handedness. Yeah, so I walked around campus that you
see Irvine, and I asked books if they knew what
it meant for a particle to be left or right handed.
So think about it for a second. If you were
approached by a physicist on a holiday morning and you
(09:33):
were asked if you knew whether particles can be left
or right handed? What would you answer? Here's what people
had to say. Do you know what it means to
say a particle can be left handed or right handed? No? No,
they don't have hands? Well is isn't it talking about
the movement of the current? Um So that's where I
can remember from physics I took on the micro level,
(09:54):
there's certain orientations and movements happen, and do there are
going too one way or the other way? But I'm
not superfamulate with outwards unfortunately, not now doing particles with hands? Well, well,
I would guess that it has something to do like
we're like the electrons around it, maybe more to the
(10:15):
blaster to the writer or something all right. Not a
lot of people knew that particles have handedness. No, No,
it a little bit of pushback, like, nope, particles do
not have hands. I thought as well, I'm gonna give
a hand to this person here. No. So not a
lot of familiarity with this concept. Yeah, which is uh,
(10:35):
I guess, I guess I know. I knew about this
idea just from talking to you, Daniel another physicists, because
I know that it's related to like the spin of particles, right,
and how they look at each other in the mirror. Yeah,
and it's related to parody. And we did a whole
fun video with Derek Mueller of Veritassium about parody and
(10:56):
charge parody and its impact on time with particles. It's
a gorgeous video. Folks out there really interested in this
concept of symmetries and particles, go check it out. I
think it's called do Particles Tell Time? On YouTube? And
so so, just to clear things up, particles don't have hands.
We we've established that, at least we don't think that
(11:17):
we've seen, right, they could have point hands, that's right.
We have to qualify what we understand here. We have
not seen particles hands. It doesn't mean they don't have them.
They could be super duper tiny cute, little tiny particle hands. Yeah,
that's how they that's how they hold on to each other,
they do how they make those bonds. Right, that's how
(11:39):
the universe is connect the tiny little hands. That's right.
But you know, you can have handedness even if you
don't have hands, and let's get into it. But I
feel like even if particles were a little spherical balls,
which I know they're not, it seems weird that they
would have like a preference between right and left, because
what's the right and left of a perfect sphere? You're
exactly right, and um, if you had a perfect sphere,
(12:02):
it's perfect sphere is not handed. Right. To have something
be handed you need at least two different directions that
you can compare. And so a perfect sphere, however, can spin,
and when it spins, the axis along which it's spinning
gives you one direction, and then you can compare that
spin direction to something else, like the direction it's moving,
(12:23):
and you can ask, like, do those two directions line up?
This kind of stuff. So particles can have handedness because
it's built on top of other properties they have. But
You're right, a sphere that has no handedness, it looks
the same in the mirror by itself. And and as well,
I guess a point as well, right, Like a point
would have even less of a less of a hand
(12:44):
unless it has plenty point hands right, which is not
really the matter at hand. But you're saying that handedness
for particles is related to you get like you got
to throw in another property into the conversation in order
to have handedness in a point particle. Yeah, And here's
where we get into murky territory, because handedness it's a
(13:08):
quantum property with particles. It's like an intrinsic property. It's
like charge right, or it's like spin it's not physically spinning,
or there is no place where the charge is. It's
just like a label we put on a particle. And
so these particles have this intrinsic leftiness or rightness really,
and we can make it connected to this other physical thing,
(13:29):
but in the end it really is deeply, fundamentally just
sort of an internal quantum label that we can never
really truly understand. Really, because I've never seen handedness in
any of the you know, posters or graphics for the
standard model of physics. You know, I see spin, I
see charge, I see color, but I never see like
left ear righty. You know. Yeah, Well it's mostly connected
(13:51):
to the weak force, because the weak forces what revealed
to us that handedness was a thing we had to
think about and that it was actually important. So I
guess we should call it quantum handedness because that's the
that's the solution to any confusion in physics is just
at a at a word that says you're right. It
(14:12):
is confusing, It's okay, don't try to understand it at
an intuitive level. It's weird. No, you're right. Quantum X.
What we mean when we say that in physics is like, well,
this is like some other weird version of X. We're
using X because it's similar kind of in some way
to the thing you're familiar with. There's an analogy that
that's maybe helpful, but it's not really the same thing. Right.
(14:34):
It's kind of like how our podcast is known for
quantum humor. That's right, only particles get it. It's neither
here nor there, but just still try to understand it.
That's right. That's what we're getting a lot of quantum
clasks and making a lot of quantum bucks. It's it's
all theoretical, Daniel. No. But in the case of particles,
(14:57):
you can sort of define this handedness by saying, let's
look at the direction it's moving, and then let's look
at the axis around which it's spinning, and ask are
those two things pointing in the same direction or not?
And so we call it right if they're in the
same direction, and left handed if they're in opposite directions.
But that's arbitrary. We could have just labeled them any way.
(15:18):
You know. We can call them alpha and beta, or
blue and red, or left and right or right and
left right. These are just labels we deside. Oh, I see.
It'd be like saying, like, some particles like to be
positive and green, and some particles like to be negative
and blue, and you might call that handedness or some
other property. Yeah, some of the properties, but this particular
(15:39):
one that we found, it turns out the universe cares about.
So you could construct all sorts of things and column handedness,
but the universe might be like, yeah, that's fine, I
don't care about that doesn't matter to me. But this
one is interesting because the universe does seem to care
it is something that is important. It changes the way
the universe treats these particles, and so it really does matter. Okay,
(16:00):
so you're saying that handedness in a particle means that
the spin of the particle is sort of a line
to its motion. Yeah, And it's a bit confusing to
think about the direction of spin because it's going in
every direction. Right, it's a spinning thing. It's turning and
turning and turning. What if I just turned my head
upside down, wouldn't it flip it on its head? Well,
(16:20):
it wouldn't change the direction of spin. Right, But so
you use your right hand, and if your fingers are
curling the direction the particle spinning, your thumb tells you
where we sort of define the direction of the spin vector,
and it's along the axis of spin. It's kind of
like a top if you're spinning a top. M I
guess you can spin a top both ways. But it's
(16:41):
kind of a screwdriver, I guess, or like a screw
it's like clockwise versus counterclockwise. Right, you have to define
one direction or the other. And we say that the
direction that you're the fingers curl on your right hand
is a certain way, and that helps us define a
certain direction. And so if the particle is moving in
the same same direction that this spin is pointing, where
(17:02):
again the spin comes from your thumb. If your fingers
curl the way the spear is spinning, we call that
a right handed particle. Really. Yeah, So parts of particles
don't have the option of moving either way, like they
always either move in the direction of spin or not
in the direction of spin. Oh, that's fascinating question. Remember
spin is quantized, right, and so you measure spin along
(17:24):
any axis. And because it's quantized either along that axis
or in the other direction, spin is not a infinitely
valued quantity. It has to be either positive or negative.
It's quantitied. It's this quantum spin. Like let's say that
spinning and the spinning direction is up. You're saying that
particles can move up and down. They have to move
up or down. You can't say the particle is spinning
(17:46):
and its spinning direction is up. That's quantum mechanically impossible
to know the complete spin direction, right, because there's three
different axes, and you can't know spin along three axis simultaneously.
Because the Heisenberg is certain principle. Oh, boy, the you
have to go the other direction. You say, all right,
which direction is my particle moving? All right? That define
some direction. Now I can ask is it spinning along
(18:08):
that direction or in the opposite direction? I see, And
that what I get if I ask it if is
it spinning in the direction of moving or not? Is
something that particles Some particles will always give you the
one answer, and other particles will always give you the
other answers. Or is it random? Like a particle can
be moving either aligned or not aligned with its spin.
(18:29):
That's what we call handedness. If a particle is right handed,
then it's moving with its spin. If it's left handed,
it's moving away from its spin. Now, some particles, like neutrinos,
you only ever see left handed neutrinos. Right handed trinos
do not exist. Other particles you can have both a
right handed version or a left handed version. Oh, I see, alright.
(18:50):
So some particles are ambidexterous. They can right with the
right or left hand. But some particles in nature are
definitely lefties or right ease. Yeah, And it's it's a
little bit more subtle than that. It's like, do you
think of the electron and the positron is different particles
or sort of two sides of the same coin in
the same way. Do we think of like the left
(19:11):
handed electron and the right handed electron is two different
particles or just sort of like two different versions of
the electron, because it turns out nature sees them as different.
So the electron can be right or left handed, or
you could say it that there are right handed electrons
and left handed electrons. Oh, I see, but is it
like fifty fifty or what is it? Um? The universe
(19:32):
prefers left handed electrons. You mean meaning there are more
of them, There are more left handed electrons. Yes, wow,
huh so it's kind of the opposite of people. No,
that's right. And also for our DNA, you know, our
d N A has a handedness to it also, and
it's also right handed. All of our organic molecules in
our body are right handed molecules. Uh. Interesting, alright, So
(19:55):
that's kind of what handedness is is um, do particles
like to move into direct in which they spin or
do they not? Or that they like to move in
the direction which they not spin. So that's a handedness
in particles. And so let's get into what that means
for the universe is prospects in Major League Baseball, whether
there are going to be drafted early or not, and
(20:19):
why it matters maybe to you and me. But first,
let's take a quick break, all right, Danniel. So you're
saying that some particles in nature, like the electron, can
(20:40):
be right or left handed, meaning they can move. You
see them moving in the direction that they're spinning, and
some of them you see them moving not in the
direction they're spinning. But some particles, like the neutrino, do
have a preference. That's exactly right. Neutrinos are only left
handed and anti neutrinos are only right handed. And this
is a really fascinating thing that we discovered only about
(21:01):
fifty years ago, that this concept of particle handedness is
a real thing in the universe. And you know, we've
been like over the history of science adding labels to
particles as we discover them, we'll we'll see something happen
and we're like, well, we can't explain that with the
labels we currently have. So maybe particles are a little
bit more complicated, like we have to add spin to them,
(21:23):
or we have to add flavor or color or whatever
to sort of have our theory have enough wrinkles in
it to describe all the weird effects that we observe,
and so handedness is like one of the latest ones.
In the late fifties, people saw these really strange experiments
where it looked like the universe didn't work the same
in the mirror as it does not in the mirror,
(21:44):
and to explain them, they had to add this new
property to particles called handedness. Oh, I see, Like, if
every particle in nature was right and left handed, we
wouldn't even have a name for it. It could just
be like, you know, it wouldn't matter. But you're saying
it's sort of does matter in the universe. Yeah, we
wouldn't know if it was real. Like you and I
could right now invent a new particle label right, call
(22:08):
its strip nous And all right, the electrons we're gonna
say are blue stripe and with red, and those electrons
are green striped with white or whatever I'm gonna go with.
Bananan is banan is. But if the universe treats particles
the same, whether or not johe has labeled them to
be banana equals one or banan equal zero, then it
doesn't matter. It's not a physical thing, right, It's just
like an idea in your mind. It's like literally another thing.
(22:29):
Like you would say, that's not a thing, dude, but
nobody cares. But let's say somebody doesn't experiment one day
and they just and they realize, you know what particles
that Joe has little labeled having banan equals one, the
universe treats differently than we'd be like, the universe is
not symmetric to banananus, and then it would be a
real physical thing. That's exactly what happened in physics. People
(22:50):
had this idea of handedness, but they thought that's ridiculous.
How could the universe prefer one to the other. Clearly
it's symmetric. There's two options there. It's just a thing
in your head. And they didn't experiment. That proved them wrong.
It was like in Clueless, where one of them the
other stopped trying to make it a thing. It's not
a thing, but it turns out it is a thing.
(23:11):
It turns out it is a thing. And you know,
there's a lot of really interesting deep philosophical questions. They're like,
how many other things are there? Of particles? That are
really exists, but we just haven't figured out either the
way the universe prefers one to the other or an
even deeper question is what if there are particle things
that the universe is just totally symmetric to so we
(23:32):
will never discover them, Like it is a thing, but
we can't tell a thing. Yeah, in which case is
it really a thing? I think that's what's happening with
the banana is of particles. You guys just can't see it,
but I know it's there. Maybe we just need a
really big accelerator once you raise fifty dollars and we'll
discover bananan this. You wouldn't go to a circle. We're
(23:52):
just going to half circle. That's right. We need to
sort about elliptical accelerator, you know the been and a curve. Yeah,
and forget and forget those cryogetic magnets. We would just
use banana appeals to lubricate the particles. It's not a
particle accelerator. It's a particle slipper. There you go. Comedy
(24:16):
would be a plentiful in this accelerator. Yeah. Okay, so
particles have a handing this and so what does that mean?
What does that mean that the universe has the preference
in some cases or not you saying You're saying it's
related to the weak force. Yeah, Well, we have all
these fundamental forces of physics, you know, the weak force,
the strong force, electromagnetism, and gravity, and they all are
(24:39):
different forces. Were trying to understand, of course, how they're related.
But they have different effects, and most of them don't
care one whit about whether a particle is left handed
or right handed. But the weak force is weird, Like
the electromagnetic force doesn't care if an electron is right
handed or or left handed. It's democratic. It treats those
two the same, and the strong force treats left handed
(25:02):
corks and right handed corks the same way. It's like,
I see you both the same, I am handedness blind.
I'm gonna attract you or force you to do something,
and I don't care. That's right. If you didn't experiment
with the strong force, and you had it set up
next to a mirror, and you watch the experiment unfolding
in the mirror, you could use the exact same laws
(25:22):
of physics that we have in our universe to describe
what you see in the mirror. Because in the mirror universe,
all the handednesses are flipped, but the strong force doesn't care.
It's like, oh, left handed corks now are now right
hand corks? I treat him the same. Oh I see
the equations kind of work out. The same equations are
perfectly symmetric, and the effects are perfectly symmetric, so flipping
them does nothing, Like what do you see in the mirror?
(25:44):
Could may as well not be in the mirror? Yes,
or you can't do an experiment to tell are you
in the mirror world or not? As the results of
the same interest. But that's not true of the weak force. Okay,
so the weak force, it's different different. It does affect
particles differently depending on this idea of handedness. That's right.
(26:06):
And it was in the fifties of people realized nobody's
ever checked to see if the weak force breaks this
rule or not. People just sort of assumed it's such
a deeply ingrained assumption, like, of course the universe doesn't
prefer one or the other. And then the theorists went
through and said, well, has anybody ever checked? And people
had checked for a electro magnetism and for the strong
(26:26):
force and all that stuff, but nobody had checked for
for the weak force, and if physicist did it, well,
I feel like there are two ways in which handedness
can matter. Like one is which are the right or
lefties do we see more of? And that's kind of interesting,
Like the fact that we see more left handed new
trinos and right handed new trinos is sort of one
(26:49):
way that the universe is a preference. But then you're
you're I feel like there's also another way in which
the universe has a presence, which is in through the forces.
Like the laws of physics actually applied differently to the
lefties or right easy, but those are the same concepts.
Right we interact with things using forces, so we only
see left handed neutrinos because we interact with them. It's
(27:10):
possible there are right handed neutrinos out there that we
can't interact with because our forces don't touch them. We
only see what we what it's visible and what we
can interact with as a whole. You know, we won't
recently discovered that there's huge parts of the universe. We
barely have hints that actually exist, and so there could
be other particles out there that are right handed neutrinos.
We haven't seen because we can't interact with them. Oh
(27:32):
I see, it's the same thing. It's the same thing.
There could they have plot thickens or um passes throughs
like neutrinos. We're not I'm not quite sure what how
people are getting this, but we're just saying that there could.
There isn't more of the left handed neutrinos in the universe.
Is just that's the only kind we see. But we
(27:53):
don't know if there are right handed neutrinos because we
can't interact with them. Therefore, we can't prove whether or
not they exist because what we us to interact with
them has a preference. It's like a filter. Now, the
other particles, electrons and quarks, we can interact with them
in other ways that are democratic, right, because the strong
force and electromagnetism doesn't prefer one or the other. Neutrinos,
(28:14):
we can only interact with them via the weak force.
Oh I see. It's the only way we can see
them and they and it certainly does prefer it. So
there could be as many right handed nutrinos out there
in the universe as left handed neutrinos. We just can't
see them because the weak force only lets us interact
with left handed ones. That's right. And you know in
(28:34):
the same way that like the space could be filled
with invisible, imperceptible bananas, we can't see them, so are
they really there? Well, we have to use the banana force,
which I've yet to discover, but I'm sure it's it's
on the horizon there. Yeah. And it's fascinating because this
effect has to do also with charge, right, because the
(28:56):
particle that mediates this thing from the weak force, the
W particle, which carries electric charge. So you have W
minuses can decay to left handed electrons and W plus
is decay to right handed positrons. Okay, so what does
that mean. It's relevant because the way we sort of
(29:17):
patched up this symmetry is by adding charge to it.
You can tell whether or not you're in the mirror world.
By doing this experiment, um to see whether things are
reversed right, whether the weak force is giving you left
handed stuff or right handed stuff. But if you in
the mirror you also flip the charge of everything, then
the experiment looks exactly the same. Okay, Well, maybe step
(29:37):
us through a little bit, like what does it mean
that the weak force prefers left handed to right hand,
like it only interact with left handed things as far
as we know, or or like it only works with
left handed things. Yeah. The w bosons in particular will
only interact with left handed matter particles or right handed
(29:59):
antimatter articles. So left handed electrons, left handed corks, left
handed neutrinos, or right handed positrons, right handed anti neutrinos,
right handed anti corks. The z the z boson, which
is another particle that communicates the weak force, is even weirder.
It will interact with both, but it prefers the left
(30:20):
hand like interacts with the left lefties more than the rightings.
Oh you're okay, now, I guess now. Now you're taking
me through the particles that mediate that like helps us
communicate these forces. Right, that's exactly right, because the weak
forces three of them. Okay, you're saying that the particles
that communicate the weak force, those are the ones that
(30:41):
have the preference. It's not like the concept of the
weak force as a preference, but the particles that communicated
have a preference. Yeah. Well, the particles, they are the
manifestations of the force. Right, we think about these particles
as doing the duty of the force the Jedi does.
The Jedi order exists without the Jedi, you know, they're
carrying out the mark in orders, the Jedi hierarchy. So well,
(31:03):
I mean, it's it's like saying like, it's not that
the police force has a preference for left handed right
hand the people. It's more like, you know, it's like
parking offers have a preference, but uh, you know, detectives
have a different preference. You know what I mean, Like,
it's it's it's it's different than saying that the whole
thing has a preference. Yeah, and you're right. And there
are three particles there, the media, the weak force, the
(31:25):
W plus, the W minus, and the Z those are
sort of like the analogies of the photon. But for
the weak force and the W plus and the W
minus they only interact with left handed particles or right
handed antiparticles. I see. It's like that's how the preference
manifests itself. It's like the messengers for this force have
(31:45):
a preference. That's why we can't communicate with right hand
the netrinos, because the messengers are kind of blinded to
that the other kind. Yeah, and that's how they discovered it.
They took a bunch of atoms and they lined up
their spins in a certain direction, and then they saw
which do direction do the particles shootout? Do the shoot
out in the same direction of the spin, in which
case they'd be right handed. Do they shoot out against
(32:06):
the direction of the spin, in which case they'd be
left handed. And they sort of expected it to be
balanced so you couldn't tell, Like they expected to get
the same number of right and left handed particles, so
that you couldn't tell if you were in the mirror world.
But what they saw was a total shocker. Not only
was it not balanced, but it was totally unbalanced, like
zero right handed particles a left handed particles were shot out.
(32:29):
And so the weak force doesn't just prefer left handed particles,
It like maximally prefers it as far as we know.
I mean, could it be producing right hand at once
that we just can't see or interact with. It could
be there could be right handed particles that we don't
interact with, but they don't interact with the weak force,
so they have to be some other new force for
us to interact with them. If they interacted via the
weak force, we would see it. Well, but I mean,
(32:51):
I guess one question is, how do we know it's
the weak forces fault or those particles is fault? Like
what if it's our fault? You know, like what if
we were parents, it's always our fault. Yeah, what do
you mean our faults? Well, I mean, like maybe maybe
there's a new kind of boson we'll call it the
(33:11):
ex boson, which does interact with the right ten particles
through the weak force, but we just don't interact with
the ex boson. Totally possible. Yeah, there could be a
whole complicated sectors of particles out there that interact with
each other but not with us, and we just haven't
seen them or haven't yet discovered them. Nobody's invited us
to the party. That's the whole hypothesis for dark matter, right.
(33:33):
We know that there's a lot of dark matter out there.
We don't know what kind of particle is it. We
don't know if it feels forces with um among those particles,
we don't know if there's like ten different dark matter
particles are always changing into each other. So there could
be a whole complicated sectors and oceans of physics there
that we are not primy tune because we don't have
like a portal into them, no way to interact with
(33:55):
anything that's happening there. Right, If only we had that
banana particle accelerator, it would open new doors to the
universe for us. It would peel away the layers hidden
from us. It would slip us into a new era
of physics. Al Right, well, that's that. That makes it
a bit clearer for me, and how the universe has
(34:16):
this preference, and so let's get into why it matters
to the universe and maybe to us. But first let's
take a quick break, all right, Daniel, So the universe
(34:37):
apparently prefers lefties. You know, I think left handed people
always have felt pretty special, is my understanding. And now
they know why, and now they know why the universe
likes you better. Yeah, well, the weakest part of the
universe at least likes them better. Oh no, that's not true.
Gravity is the weakest force. Week the weak forse just
sort of has that name. But it it's fascinating, you know,
(35:01):
not only that the universe is asymmetric that seems to
notice that there's a handedness, but that it prefers this one,
and you can wonder, like, why don't we live in
a universe that's asymmetric the other way that prefers right
handed particles right where the weak force interacts only with
the right handed particles. It's this kind of arbitrary seeming
(35:22):
choice that makes us wonder about like the multiverse right, well, um,
meaning like maybe it's weird that it has a preference,
So there must be a twin out there who is
right handed. Well, that's the symmetry in your brain screaming
out for an explanation, right, I think there must be balanced,
but there doesn't have to be. You know, imagine you're
at the control panel of the universe in the first
(35:44):
moment of the Big Bang, when the laws of physics
are being set in stone, and you have to choose
left handed or right handed universe. You know, how is
that choice made? Are there a billion universes out there
and it's randomly assigned for each one, or is there
some deep underlying principle of physics that demand hands that
the weak force be left handed? There could be no
other way? Or could they could it just flip the coin?
(36:06):
It could be We we don't know, Like according to
our current understanding, you could write consistent laws of physics
where the weak force um prefers them equally, or the
weak force prefers only right handed particles, or were prefers
one by a little bit. We don't understand why it
is this way. Does it have to be this way?
We have no reason to believe it has to be
(36:27):
this way, and yet it is so. That seems to
me like a clue. Right, do we know in people
why some people are left handed or right handed? And
does it depend on genes or is it just some
random process um Well, based on my deep expertise in
biology from being married to biologists, is she right handed
or left hand? She's right handed, but we have some
(36:47):
lefties in her family. There's actually two layers of answer there.
One is people like what they prefer to write with,
and we're mostly right handed. We don't know why, And
it's again a great question, like was that just an
arbitrary choice that the brain decided to specialize and this
side of the brain is better at this, and the
other side of the brain is better at that, And
maybe there were equal populations at some point and then
(37:08):
it just sort of randomly drifted in one direction. We
just don't know. Um. And then there's this deeper question
about the chirality of molecules in life. All the molecules
in life, including d NA, have a corality that's right handed,
which means they have the same sort of um orientation
when you rotate the object right and like molecules have
(37:31):
a mirror image version of themselves too. Precisely, every single
organic molecules right handed. And if you were fed like
food made out of left handed molecules, you couldn't eat it,
like they die, you cannot process it. And so that's
another just like seems like an arbitrary choice could have
(37:51):
been something else. Um, we don't understand any of these things.
And I don't know if the if the mystery of
particle physics handedness is connected to those at all, because
it's definitely the other direction, or if this is just
sort of a mathematical connection where you can identify handedness
and sort of see a similarity in the sort of question. Well,
I see, huh, Like, um, like everything that might be
(38:12):
possible would have a handedness preference or something like biology
particles you know, like just a fundamental you know, property
of of existing. Yeah, but it makes our universe interesting,
and for example, the reason why the weak force is
so weird and so left handed is one of the
(38:33):
reasons why the Higgs boson is so fascinating. What do
you mean, Well, the Higgs boson, what it does is
it connects the left and right handed particles together to
give them mass. It interacts with the left and the right.
It touches, it talks to both of them, and to
talking to them together is how it gives those particles mass.
And neutrinos we don't know. We think they have mass,
(38:55):
but we don't quite really know how much mass they
have and how they get the mass, and do they
get it from the Higgs boson or not. It's a
whole bit complicated question. But the Higgs, it treats the
left and the right totally equally and sort of combines
them into one combined particle that has a specific mass. Right,
But I guess the main point is that the universe
has a preference for left or right hand. It is,
(39:16):
it seems, but we don't know why it has that preference. Right,
it's a big mystery. Right, And it's weird. Yeah, it
is weird. And if it wasn't for this little effect
in the weak force, which took a long time to discover.
We wouldn't even know, so it could have been that,
you know what if the weak force was totally symmetric
for some weird reason. Particles have handedness, but we didn't
(39:38):
even know, like that they have this property, Well, we
wouldn't care, I guess, right, I care? I care. I
want to know the truth, man, not just what's relevant
for some excises. You want to see all the features,
even if you can't see the features, of course. I
want to know what does it mean to be a particle?
All right? What are the number of labels you need
to define a particle? Mass, spin, charged, color, flavor? Why
(40:01):
all those things? What do they mean? Why this and
why not that? Why not bananimists? To me, these are
really deep, fascinating questions about like the very nature of
the universe. So yeah, I want to know, Like if
you found out half of all particles had an asterisk
next appin to them, But no, it didn't matter at
all for anything else, Like nobody would care, but you
would care me and all the other particle physicists in
(40:24):
the world, and anybody who cared about understanding the nature
of reality. But yeah, you're right. Nobody else you like,
why does that have an asterisk? I see, all right,
well I want to know why the universe has an asterisk?
All right? Well, I think this is all just a
big lesson on ways in which we explore the universe.
You know, we look for interesting phenomenon and interesting preferences
(40:48):
that the universe has, and that tells us something about
how it's all put together. Yeah, and we don't understand
the importance um and the ramifications sometimes of these things.
Like people thought about particle handedness as sort of an
abstract idea a hundred years ago when particles were first
being understood. They thought, now, whatever, it's just a mathematical curiosity.
It's not relevant, and then later turned out to be relevant,
(41:10):
and it might even turn out to be more relevant.
Maybe we'll discover a new force that's very powerful and
does prefers left to right or right to left or
something like that. So it's it's worth just sort of
like exploring and trying to understand because you never know
where the next big discovery is going to be. Yeah,
it would be pretty cool. Would you like Daniel to
have a hand in that discovery? Only, but only if
(41:34):
it's a left hand. I'd like to discover it. And
then I've got like you to give me a hand
when I did. You'd like to get both your hands
on this discovery. I just want to get my hands dirty, okay.
And that with that, we've exhausted all the bad puns, Daniel,
so maybe we should wrap it up. That's right, we've
done all the left handed punts and the right handed punts. Well,
(41:55):
thank you all for listening to me. This is a
fascinating question about the sort of deep nature of the universe,
us in this stuff that makes it up, and how
we understand it in terms of our macroscopic ways of thinking,
flavor of color, spin, and now left handedness and right handedness. Yeah,
so we hope you enjoyed that. Thanks for joining us.
On the other hand, we're not done yet. We're gonna
(42:15):
do the mirror mirror image of this podcast episode, but
the whole thing backwards, the back course, and we'll say
the universe has a preference for right handed particles. We've
got to do it backwards and positively charged. And where
the jokes are good this time, that's right, where I
(42:37):
make the jokes and you laugh at them all right,
Thanks everyone for tuning in, and I hope that podcast
reached a parody of our other ones and it's not
a parody of itself. See you next time. Before you
still have a question after listening to all these explanations,
(42:58):
please drop us a line and we'd love to hear
from you. You can find us on Facebook, Twitter, and
Instagram at Daniel and Jorge That's one Word, or email
us at Feedback at Daniel and Jorge dot com. Thanks
for listening and remember that Daniel and Jorge Explain the
Universe is a production of I Heart Radio. For more
podcast from my Heart Radio, visit the I heart Radio app,
(43:20):
Apple Podcasts, or wherever you listen to your favorite shows.
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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